Influence of Polyamide Morphology on the Fouling Propensity of Thin-Film Composite Forward Osmosis Membranes: Importance of the Underlying Support Layer Surface Structure

摘要

Fouling has been identified as a primary challenge for the use of polyamide-based thin-film composite (TFC) membranes in real-world applications of reverse osmosis, forward osmosis (FO), and pressure-retarded osmosis. Membranes with a higher propensity for fouling experience flux declines that severely reduce process efficiency. In this study, we sought an explanation for observed differences in flux decline and flux recovery of two types of membranes during FO fouling experiments. Membranes were fabricated by easting a microporous layer of polysulfone on a non-woven polyester fabric via phase separation, over which the selective polyamide layer was formed via interfacial polymerization. The solution used in phase separation was 12% polysulfone in either dimethylformamide (DMF) or n-methyl-2-pyrrolidinone (NMP); this was the only difference between the two sets of membranes. When exposed to a simulated wastewater feed solution containing alginate during FO experiments, the membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) and greater recovery of flux during physical cleaning (98.52 ± 0.65% recovery of the initial flux) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 + 2.62% flux decline and 96.14 + 0.54% flux recovery). A clear difference in fouling propensity has not been reported previously for membranes fabricated using identical interfacial polymerization procedures performed on slightly different support structures.